HP -15C Advanced Functions Handbook page 74

72 Section3: Calculating in Complex Mode
.
-1
0 1
*/yy
*
The principal branches in the last four graphs above are obtained
from the equations shown, but don't necessarily use the principal
branches of ln(2) and \[z~ .
The remaining inverse functions may be determined from the
illustrations above and the following equations:
= LN(2)/LN(10)
To determine all values of an inverse relation, use the following
expressions to derive these values from the principal value
calculated by the HP-15C. In these expressions, k= 0, ±1, ±2, ... .
1
(
2
) +krr
z) = (-1)* SINH-
1
^) + ikir
cosh-
1
(2) - iCOSH'Hz) + iZkir
tanh-
l
(2) = TANH'^a) + ikir
u? =
Wz
e
i2nkz